Examinando por Autor "Luarte Anduaga, Thais"

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    Destino ambiental de los Contaminantes Orgánicos Persistentes (COP) durante el verano austral en la Antártica
    (Universidad Andrés Bello, 2023) Luarte Anduaga, Thais; Galbán-Malagón, Cristóbal; Pulgar Aguila, José
    This study investigated the environmental fate of Antarctica's persistent organic pollutants (POPs). These anthropogenic compounds are stable, resistant to degradation, and can bioaccumulate in organisms and biomagnify through the food chain. The fate of persistent organic pollutants (POPs) in the environment depends on their chemical properties and the exchange processes between different compartments. In particular, the air-water exchange is important in aquatic systems, affecting POP levels through atmospheric volatilization and deposition. Once POPs reach the water, they may remain dissolved, volatilize again, or bind to particles such as phytoplankton. These contaminants can follow different environmental pathways, including transfer to higher trophic levels, resulting in biomagnification, export to deep water, and subsequent inclusion in the biological pump. In Antarctica, there needs to be more information on these processes, although the polar regions act as ultimate sinks for POPs. It has been observed that during periods of high productivity, POPs are transferred to sediments due to high biological pump fluxes and accumulation in living organisms. However, previous studies in Antarctica have had limitations in accurately quantifying POP levels due to samples taken at different locations. In addition, the assessment of POP cycling in aquatic systems has been conducted regarding organic carbon, which has left uncertainty about the fate of POPs in the Southern Ocean. Therefore, the main objective of this study was to assess the environmental fate of POPs, such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), during periods of blooms in Antarctica. Simultaneous air, water, phytoplankton, and zooplankton sampling was conducted in Fildes Bay, King George Island, Antarctica, from December 2019 to January 2020. Several factors were calculated, such as air-water exchange and bioaccumulation, bioconcentration, and biomagnification factors. In addition, the atmospheric halflife was estimated using characteristic decay times (TD), where we observed that HCB levels in the Antarctic atmosphere were higher than those of the other target OCs. However, HCB also showed greater fluctuations and did not significantly decrease over time. In contrast, atmospheric levels of HCH and some DDT and PCBs have decreased significantly. The estimated atmospheric half-lives of persistent organic pollutants (POPs) vary by compound. For DDT compounds, the half-lives are 4.4' DDE (13.5 years), 4.4' DDD (12.8 years), and 4.4' DDT (7.4 years). For HCH compounds, the half-lives are 2.4' DDE (6.4 years), 2.4' DDT (6.3 years), α-HCH (6 years), HCB (6 years), and γ-HCH (4.2 years). For PCB congeners, half-lives decrease in the following order: PCB 153 (7.6 years), PCB 138 (6.5 years), PCB 101 (4.7 years), PCB 180 (4.6 years), PCB 28 (4 years), PCB 52 (3.7 years) and PCB 118 (3.6 years). These estimates show the persistence of POPs in the atmosphere and their ability to remain in the environment for long periods. In the case of HCH isomers and PCBs, the ban on POPs imposed by the Stockholm Convention has reduced their levels in recent decades. However, their ubiquity in the Antarctic atmosphere shows the problems associated with highly persistent synthetic chemicals. The results showed that hexachlorobenzene (HCB) was the most abundant compound in air and water. Significant concentrations of PCB 11 were also found in air and seawater. The estimated fugacity gradient for PCB compounds indicates a predominance of net atmospheric deposition for HCB, α-HCH, γ-HCH, 4,4'-DDDT, 4,4'-DDE, and close to equilibrium for the compound PeCB. The observed deposition of some OCs may be due to high biodegradation rates and sedimentation fluxes contributing to the decrease of these compounds in surface waters, supported by the measured ability of the microbial consortium to degrade some of these compounds. Estimated fugacity gradients for PCBs showed differences between congeners, with net volatilization predominating for PCB-9, a trend close to equilibrium for PCB congeners 11, 28, 52, 101, 118, 138, and 153, and deposition for PCB 180. Snow amplification may play an essential role in decreasing PCBs in surface waters. Snow amplification may play an important role in less hydrophobic PCBs, with volatilization predominating after snow/glacier melting. As hydrophobicity increases, the biological pump decreases the concentration of PCBs in seawater, reversing the fugacity gradient toward atmospheric deposition. Finally, regarding the levels detected in plankton, we recorded high concentrations of HCB in phytoplankton and of the congener PCB 11 in zooplankton, elucidating for the first time the presence of this congener in Antarctic biota high concentrations. On the other hand, BCF and BAF estimates of OCP and PCB show a direct and significant linear relationship with Log KOW, evidencing a trend of equilibrium or near equilibrium between water and phytoplankton and between water and zooplankton, respectively. BAF and BCF values were in a similar range, indicating that, in this study, zooplankton did not accumulate POPs from phytoplankton grazing, in agreement with the BMF values obtained, where most of the analyzed compounds show values lower than 1, indicating no or low biomagnification. According to the results, an effective and significant transfer of OCPs and PCBs from water to phytoplankton and from water to zooplankton was obtained. However, there was no effective and significant transfer between phytoplankton and zooplankton. Overall, the study highlights the importance of continued monitoring, regulating atmospheric sources, and understanding the environmental fate of POPs in Antarctica. Coordinated efforts are needed among countries with an Antarctic presence to establish monitoring networks similar to those in the Arctic to ensure comprehensive assessment and protection of the region's ecosystem.